From bb9371f255c808659066f6eae70dbcbb36e3f45e Mon Sep 17 00:00:00 2001
From: Sam Rawlins <srawlins@google.com>
Date: Thu, 9 Feb 2023 22:41:19 +0000
Subject: [PATCH] [analyzer] Tidy up much benchmark and integration test code:

* Add a type argument to raw `Future` types (typically `Future<void>`)
* Add type arguments to raw `Map` types (typically Map<String, Object?>`)
* Add a type argument to raw `Completer` constructor calls.
* Use collection-elements in more places.
* Replace an implementation of `String.padLeft` and `String.padRight` with
  StringBuffer extension methods that use `String.padLeft` and
  `String.padRight`.
* Rename many `sb` variables to `buffer`, which is more idiomatic.
* Move some StringBuffer helper methods to be extensions on StringBuffer.
* Use constructor tear-offs instead of closures which call a constructor.
* Use single quotes where we can.
* Do not prefix constant names with the letter 'k' [1].
* In IntegrationTestMixin:
  * Rename to `IntegrationTest`, as it is never used as a mixin.
  * Public Stream fields are converted to be getters.
  * Private StreamController fields are initialized at their declaration [2],
    instead of an initialization method.
* Remove empty zero-parameter constructors.

[1] https://dart.dev/guides/language/effective-dart/style#dont-use-prefix-letters
[2] https://dart.dev/guides/language/effective-dart/usage#do-initialize-fields-at-their-declaration-when-possible

Change-Id: I7a923a80d32f74fbecf42a0fa35ae25285994097
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/281874
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
---
 pkg/analysis_server/benchmark/benchmarks.dart |  35 ++-
 .../benchmark/integration/driver.dart         | 141 +++++-----
 .../benchmark/integration/operation.dart      |   4 +-
 .../benchmark/perf/benchmarks_impl.dart       |   8 +-
 .../benchmark/perf/dart_analyze.dart          |  26 +-
 .../perf/flutter_completion_benchmark.dart    |  14 +-
 .../benchmark/perf/memory_tests.dart          |  12 +-
 .../execution/delete_context_test.dart        |   2 +-
 .../support/integration_test_methods.dart     | 256 ++++++++----------
 .../support/integration_tests.dart            |   9 +-
 .../test/timing/timing_framework.dart         |  16 +-
 .../tool/spec/codegen_inttest_methods.dart    |  34 +--
 12 files changed, 241 insertions(+), 316 deletions(-)

diff --git a/pkg/analysis_server/benchmark/benchmarks.dart b/pkg/analysis_server/benchmark/benchmarks.dart
index eecb3c6182e..9d4aed2fbcb 100644
--- a/pkg/analysis_server/benchmark/benchmarks.dart
+++ b/pkg/analysis_server/benchmark/benchmarks.dart
@@ -77,9 +77,9 @@ abstract class Benchmark {
 
   bool get needsSetup => false;
 
-  Future oneTimeCleanup() => Future.value();
+  Future<void> oneTimeCleanup() => Future.value();
 
-  Future oneTimeSetup() => Future.value();
+  Future<void> oneTimeSetup() => Future.value();
 
   Future<BenchMarkResult> run({
     required String dartSdkPath,
@@ -87,7 +87,7 @@ abstract class Benchmark {
     bool verbose = false,
   });
 
-  Map toJson() =>
+  Map<String, Object?> toJson() =>
       {'id': id, 'description': description, 'enabled': enabled, 'kind': kind};
 
   @override
@@ -106,7 +106,7 @@ class BenchMarkResult {
     return BenchMarkResult(kindName, math.min(value, other.value));
   }
 
-  Map toJson() => {kindName: value};
+  Map<String, Object?> toJson() => {kindName: value};
 
   @override
   String toString() => '$kindName: $value';
@@ -124,35 +124,32 @@ class CompoundBenchMarkResult extends BenchMarkResult {
   }
 
   @override
-  BenchMarkResult combine(BenchMarkResult other) {
+  BenchMarkResult combine(covariant CompoundBenchMarkResult other) {
     BenchMarkResult combine(BenchMarkResult? a, BenchMarkResult? b) {
       if (a == null) return b!;
       if (b == null) return a;
       return a.combine(b);
     }
 
-    var o = other as CompoundBenchMarkResult;
-
     var combined = CompoundBenchMarkResult(name);
-    var keys = (<String>{}
-          ..addAll(results.keys)
-          ..addAll(o.results.keys))
-        .toList();
+    var keys = {
+      ...results.keys,
+      ...other.results.keys,
+    }.toList();
 
     for (var key in keys) {
-      combined.add(key, combine(results[key], o.results[key]));
+      combined.add(key, combine(results[key], other.results[key]));
     }
 
     return combined;
   }
 
   @override
-  Map toJson() {
-    var m = <String, dynamic>{};
-    for (var entry in results.entries) {
-      m['$name-${entry.key}'] = entry.value.toJson();
-    }
-    return m;
+  Map<String, Object?> toJson() {
+    return {
+      for (var entry in results.entries)
+        '$name-${entry.key}': entry.value.toJson(),
+    };
   }
 
   @override
@@ -186,7 +183,7 @@ class ListCommand extends Command {
   @override
   void run() {
     if (argResults!['machine'] as bool) {
-      var map = <String, dynamic>{
+      var map = <String, Object?>{
         'benchmarks': benchmarks.map((b) => b.toJson()).toList()
       };
       print(JsonEncoder.withIndent('  ').convert(map));
diff --git a/pkg/analysis_server/benchmark/integration/driver.dart b/pkg/analysis_server/benchmark/integration/driver.dart
index 5c16d36a6c3..b8b79c5e15c 100644
--- a/pkg/analysis_server/benchmark/integration/driver.dart
+++ b/pkg/analysis_server/benchmark/integration/driver.dart
@@ -13,28 +13,10 @@ import '../../test/integration/support/integration_test_methods.dart';
 import '../../test/integration/support/integration_tests.dart';
 import 'operation.dart';
 
-final SPACE = ' '.codeUnitAt(0);
-
-void _printColumn(StringBuffer sb, String text, int keyLen,
-    {bool rightJustified = false}) {
-  if (!rightJustified) {
-    sb.write(text);
-    sb.write(',');
-  }
-  for (var i = text.length; i < keyLen; ++i) {
-    sb.writeCharCode(SPACE);
-  }
-  if (rightJustified) {
-    sb.write(text);
-    sb.write(',');
-  }
-  sb.writeCharCode(SPACE);
-}
-
 /// [Driver] launches and manages an instance of analysis server,
 /// reads a stream of operations, sends requests to analysis server
 /// based upon those operations, and evaluates the results.
-class Driver extends IntegrationTestMixin {
+class Driver extends IntegrationTest {
   /// The amount of time to give the server to respond to a shutdown request
   /// before forcibly terminating it.
   static const Duration SHUTDOWN_TIMEOUT = Duration(seconds: 5);
@@ -63,30 +45,33 @@ class Driver extends IntegrationTestMixin {
   Future<Results> get runComplete => _runCompleter.future;
 
   /// Perform the given operation.
+  ///
   /// Return a [Future] that completes when the next operation can be performed,
   /// or `null` if the next operation can be performed immediately
   Future<void>? perform(Operation op) {
     return op.perform(this);
   }
 
-  /// Send a command to the server.  An 'id' will be automatically assigned.
-  /// The returned [Future] will be completed when the server acknowledges the
-  /// command with a response.  If the server acknowledges the command with a
-  /// normal (non-error) response, the future will be completed with the
-  /// 'result' field from the response.  If the server acknowledges the command
-  /// with an error response, the future will be completed with an error.
+  /// Send a command to the server.
+  ///
+  /// An 'id' will be automatically assigned. The returned [Future] will be
+  /// completed when the server acknowledges the command with a response.  If
+  /// the server acknowledges the command with a normal (non-error) response,
+  /// the future will be completed with the 'result' field from the response.
+  /// If the server acknowledges the command with an error response, the future
+  /// will be completed with an error.
   Future<Map<String, Object?>?> send(
       String method, Map<String, dynamic> params) {
     return server.send(method, params);
   }
 
   /// Launch the analysis server.
+  ///
   /// Return a [Future] that completes when analysis server has started.
-  Future startServer() async {
+  Future<void> startServer() async {
     logger.log(Level.FINE, 'starting server');
-    initializeInttestMixin();
     server = Server();
-    var serverConnected = Completer();
+    var serverConnected = Completer<void>();
     onServerConnected.listen((_) {
       logger.log(Level.FINE, 'connected to server');
       serverConnected.complete();
@@ -107,7 +92,7 @@ class Driver extends IntegrationTestMixin {
   }
 
   /// Shutdown the analysis server if it is running.
-  Future stopServer([Duration timeout = SHUTDOWN_TIMEOUT]) async {
+  Future<void> stopServer([Duration timeout = SHUTDOWN_TIMEOUT]) async {
     if (running) {
       logger.log(Level.FINE, 'requesting server shutdown');
       // Give the server a short time to comply with the shutdown request; if it
@@ -165,19 +150,19 @@ class Measurement {
     var variance = differenceFromMeanSquared / count;
     var standardDeviation = sqrt(variance).round();
 
-    var sb = StringBuffer();
-    _printColumn(sb, tag, keyLen);
-    _printColumn(sb, count.toString(), 6, rightJustified: true);
-    _printColumn(sb, errorCount.toString(), 6, rightJustified: true);
-    _printColumn(sb, unexpectedResultCount.toString(), 6, rightJustified: true);
-    _printDuration(sb, Duration(microseconds: meanTime));
-    _printDuration(sb, time90th);
-    _printDuration(sb, time99th);
-    _printDuration(sb, Duration(microseconds: standardDeviation));
-    _printDuration(sb, minTime);
-    _printDuration(sb, maxTime);
-    _printDuration(sb, Duration(microseconds: totalTimeMicros));
-    print(sb.toString());
+    var buffer = StringBuffer();
+    buffer.writePadRight(tag, keyLen);
+    buffer.writePadLeft(count.toString(), 6);
+    buffer.writePadLeft(errorCount.toString(), 6);
+    buffer.writePadLeft(unexpectedResultCount.toString(), 6);
+    buffer.writeDuration(Duration(microseconds: meanTime));
+    buffer.writeDuration(time90th);
+    buffer.writeDuration(time99th);
+    buffer.writeDuration(Duration(microseconds: standardDeviation));
+    buffer.writeDuration(minTime);
+    buffer.writeDuration(maxTime);
+    buffer.writeDuration(Duration(microseconds: totalTimeMicros));
+    print(buffer.toString());
   }
 
   void record(bool success, Duration elapsed) {
@@ -190,15 +175,10 @@ class Measurement {
   void recordUnexpectedResults() {
     ++unexpectedResultCount;
   }
-
-  void _printDuration(StringBuffer sb, Duration duration) {
-    _printColumn(sb, duration.inMilliseconds.toString(), 15,
-        rightJustified: true);
-  }
 }
 
-/// [Results] contains information gathered by [Driver]
-/// while running the analysis server
+/// [Results] contains information gathered by [Driver] while running the
+/// analysis server.
 class Results {
   Map<String, Measurement> measurements = <String, Measurement>{};
 
@@ -236,7 +216,7 @@ class Results {
       }
     }
 
-    /// TODO(danrubel) *** print warnings if driver caches are not empty ****
+    // TODO(danrubel): print warnings if driver caches are not empty.
     print('''
 
 (1) uxr = UneXpected Results or responses received from the server
@@ -259,31 +239,46 @@ class Results {
     measurements[tag]!.recordUnexpectedResults();
   }
 
-  void _printGroupHeader(String groupName, int keyLen) {
-    var sb = StringBuffer();
-    _printColumn(sb, groupName, keyLen);
-    _printColumn(sb, 'count', 6, rightJustified: true);
-    _printColumn(sb, 'error', 6, rightJustified: true);
-    _printColumn(sb, 'uxr(1)', 6, rightJustified: true);
-    sb.write('  ');
-    _printColumn(sb, 'mean(2)', 15);
-    _printColumn(sb, '90th', 15);
-    _printColumn(sb, '99th', 15);
-    _printColumn(sb, 'std-dev', 15);
-    _printColumn(sb, 'minimum', 15);
-    _printColumn(sb, 'maximum', 15);
-    _printColumn(sb, 'total', 15);
-    print(sb.toString());
+  static void _printGroupHeader(String groupName, int keyLength) {
+    var buffer = StringBuffer();
+    buffer.writePadRight(groupName, keyLength);
+    buffer.writePadLeft('count', 6);
+    buffer.writePadLeft('error', 6);
+    buffer.writePadLeft('uxr(1)', 6);
+    buffer.write('  ');
+    buffer.writePadRight('mean(2)', 15);
+    buffer.writePadRight('90th', 15);
+    buffer.writePadRight('99th', 15);
+    buffer.writePadRight('std-dev', 15);
+    buffer.writePadRight('minimum', 15);
+    buffer.writePadRight('maximum', 15);
+    buffer.writePadRight('total', 15);
+    print(buffer.toString());
   }
 
-  void _printTotals(int keyLen, int totalCount, int totalErrorCount,
+  static void _printTotals(int keyLength, int totalCount, int totalErrorCount,
       int totalUnexpectedResultCount) {
-    var sb = StringBuffer();
-    _printColumn(sb, 'Totals', keyLen);
-    _printColumn(sb, totalCount.toString(), 6, rightJustified: true);
-    _printColumn(sb, totalErrorCount.toString(), 6, rightJustified: true);
-    _printColumn(sb, totalUnexpectedResultCount.toString(), 6,
-        rightJustified: true);
-    print(sb.toString());
+    var buffer = StringBuffer();
+    buffer.writePadRight('Totals', keyLength);
+    buffer.writePadLeft(totalCount.toString(), 6);
+    buffer.writePadLeft(totalErrorCount.toString(), 6);
+    buffer.writePadLeft(totalUnexpectedResultCount.toString(), 6);
+    print(buffer.toString());
+  }
+}
+
+extension on StringBuffer {
+  void writeDuration(Duration duration) {
+    writePadLeft(duration.inMilliseconds.toString(), 15);
+  }
+
+  void writePadLeft(String text, int keyLength) {
+    write(text.padLeft(keyLength, ' '));
+    write(' ');
+  }
+
+  void writePadRight(String text, int keyLength) {
+    write(text.padRight(keyLength, ' '));
+    write(' ');
   }
 }
diff --git a/pkg/analysis_server/benchmark/integration/operation.dart b/pkg/analysis_server/benchmark/integration/operation.dart
index 882c15fb638..569092b4f95 100644
--- a/pkg/analysis_server/benchmark/integration/operation.dart
+++ b/pkg/analysis_server/benchmark/integration/operation.dart
@@ -170,14 +170,14 @@ class ResponseOperation extends Operation {
 
 class StartServerOperation extends Operation {
   @override
-  Future perform(Driver driver) {
+  Future<void> perform(Driver driver) {
     return driver.startServer();
   }
 }
 
 class WaitForAnalysisCompleteOperation extends Operation {
   @override
-  Future perform(Driver driver) {
+  Future<void> perform(Driver driver) {
     var start = DateTime.now();
     driver.logger.log(Level.FINE, 'waiting for analysis to complete');
     late StreamSubscription<ServerStatusParams> subscription;
diff --git a/pkg/analysis_server/benchmark/perf/benchmarks_impl.dart b/pkg/analysis_server/benchmark/perf/benchmarks_impl.dart
index 48584d262d3..67b27442b39 100644
--- a/pkg/analysis_server/benchmark/perf/benchmarks_impl.dart
+++ b/pkg/analysis_server/benchmark/perf/benchmarks_impl.dart
@@ -76,7 +76,7 @@ class AnalysisBenchmark extends Benchmark {
     var completionCount = 0;
     var stopwatch = Stopwatch()..start();
 
-    Future complete(int offset) async {
+    Future<void> complete(int offset) async {
       await test.complete(filePath, offset, isWarmUp: false);
       completionCount++;
     }
@@ -191,10 +191,10 @@ class ColdAnalysisBenchmark extends Benchmark {
 }
 
 class ServerBenchmark {
-  static final das = ServerBenchmark('analysis-server', 'Analysis Server',
-      () => AnalysisServerBenchmarkTest());
+  static final das = ServerBenchmark(
+      'analysis-server', 'Analysis Server', AnalysisServerBenchmarkTest.new);
   static final lsp = ServerBenchmark('lsp-analysis-server',
-      'LSP Analysis Server', () => LspAnalysisServerBenchmarkTest());
+      'LSP Analysis Server', LspAnalysisServerBenchmarkTest.new);
   final String id;
 
   final String name;
diff --git a/pkg/analysis_server/benchmark/perf/dart_analyze.dart b/pkg/analysis_server/benchmark/perf/dart_analyze.dart
index 234e7081168..205a5815b80 100644
--- a/pkg/analysis_server/benchmark/perf/dart_analyze.dart
+++ b/pkg/analysis_server/benchmark/perf/dart_analyze.dart
@@ -120,15 +120,15 @@ class CmdLineSeveralProjectsBenchmark extends AbstractCmdLineBenchmark {
 
   @override
   List<String> analyzeWhat(bool quick) => quick
-      ? ["meta"]
+      ? ['meta']
       : [
-          "analysis_server",
-          "analysis_server_client",
-          "analyzer",
-          "analyzer_cli",
-          "analyzer_plugin",
-          "analyzer_utilities",
-          "_fe_analyzer_shared",
+          'analysis_server',
+          'analysis_server_client',
+          'analyzer',
+          'analyzer_cli',
+          'analyzer_plugin',
+          'analyzer_utilities',
+          '_fe_analyzer_shared',
         ];
 }
 
@@ -144,7 +144,7 @@ class CmdLineSmallFileBenchmark extends AbstractCmdLineBenchmark {
   String get workingDir => _tempDir!.path;
 
   @override
-  List<String> analyzeWhat(bool quick) => ["t.dart"];
+  List<String> analyzeWhat(bool quick) => ['t.dart'];
 
   @override
   void cleanup() {
@@ -154,12 +154,12 @@ class CmdLineSmallFileBenchmark extends AbstractCmdLineBenchmark {
 
   @override
   void setup() {
-    var dir = Directory.systemTemp.createTempSync("analyzer-benchmark");
-    var file = File.fromUri(dir.uri.resolve("t.dart"));
-    file.writeAsStringSync("""
+    var dir = Directory.systemTemp.createTempSync('analyzer-benchmark');
+    var file = File.fromUri(dir.uri.resolve('t.dart'));
+    file.writeAsStringSync('''
 void main() {
   print("Hello, world!");
-}""");
+}''');
     _tempDir = dir;
   }
 }
diff --git a/pkg/analysis_server/benchmark/perf/flutter_completion_benchmark.dart b/pkg/analysis_server/benchmark/perf/flutter_completion_benchmark.dart
index 12adde90930..7a6ea9afcf4 100644
--- a/pkg/analysis_server/benchmark/perf/flutter_completion_benchmark.dart
+++ b/pkg/analysis_server/benchmark/perf/flutter_completion_benchmark.dart
@@ -13,12 +13,12 @@ import 'memory_tests.dart';
 class FlutterCompletionBenchmark extends Benchmark implements FlutterBenchmark {
   static final das = FlutterCompletionBenchmark(
     'das',
-    () => AnalysisServerBenchmarkTest(),
+    AnalysisServerBenchmarkTest.new,
   );
 
   static final lsp = FlutterCompletionBenchmark(
     'lsp',
-    () => LspAnalysisServerBenchmarkTest(),
+    LspAnalysisServerBenchmarkTest.new,
   );
 
   final AbstractBenchmarkTest Function() testConstructor;
@@ -240,20 +240,20 @@ class FlutterCompletionBenchmark extends Benchmark implements FlutterBenchmark {
     // Perform warm-up.
     // The cold start does not matter.
     // The sustained performance is much more important.
-    const kWarmUpCount = 5;
-    for (var i = 0; i < kWarmUpCount; i++) {
+    const warmUpCount = 5;
+    for (var i = 0; i < warmUpCount; i++) {
       await perform(isWarmUp: true);
     }
 
-    const kRepeatCount = 5;
+    const repeatCount = 5;
     final timer = Stopwatch()..start();
-    for (var i = 0; i < kRepeatCount; i++) {
+    for (var i = 0; i < repeatCount; i++) {
       await perform(isWarmUp: false);
     }
 
     await test.closeFile(filePath);
 
-    return timer.elapsedMicroseconds ~/ kRepeatCount;
+    return timer.elapsedMicroseconds ~/ repeatCount;
   }
 }
 
diff --git a/pkg/analysis_server/benchmark/perf/memory_tests.dart b/pkg/analysis_server/benchmark/perf/memory_tests.dart
index 2c79645e821..087746159b3 100644
--- a/pkg/analysis_server/benchmark/perf/memory_tests.dart
+++ b/pkg/analysis_server/benchmark/perf/memory_tests.dart
@@ -274,21 +274,21 @@ class ServiceProtocol {
     var id = '${++_id}';
     var completer = Completer<Map>();
     _completers[id] = completer;
-    var m = <String, dynamic>{
+    var messageMap = <String, dynamic>{
       'jsonrpc': '2.0',
       'id': id,
       'method': method,
-      'args': args
+      'args': args,
+      'params': args,
     };
-    m['params'] = args;
-    var message = jsonEncode(m);
+    var message = jsonEncode(messageMap);
     socket.add(message);
     return completer.future;
   }
 
-  Future dispose() => socket.close();
+  Future<void> dispose() => socket.close();
 
-  void _handleMessage(dynamic message) {
+  void _handleMessage(Object? message) {
     if (message is! String) {
       return;
     }
diff --git a/pkg/analysis_server/test/integration/execution/delete_context_test.dart b/pkg/analysis_server/test/integration/execution/delete_context_test.dart
index 138cdaf459e..54f621f30e5 100644
--- a/pkg/analysis_server/test/integration/execution/delete_context_test.dart
+++ b/pkg/analysis_server/test/integration/execution/delete_context_test.dart
@@ -27,7 +27,7 @@ class DeleteContextTest extends AbstractAnalysisServerIntegrationTest {
         await sendExecutionMapUri(contextId, uri: 'package:test/main.dart');
     expect(result.file, pathname);
 
-    expect(await sendExecutionDeleteContext(contextId), isNull);
+    await sendExecutionDeleteContext(contextId);
 
     // After the delete, expect this to fail.
     try {
diff --git a/pkg/analysis_server/test/integration/support/integration_test_methods.dart b/pkg/analysis_server/test/integration/support/integration_test_methods.dart
index 9b0e23e35b4..b9ce0fcd0b7 100644
--- a/pkg/analysis_server/test/integration/support/integration_test_methods.dart
+++ b/pkg/analysis_server/test/integration/support/integration_test_methods.dart
@@ -11,14 +11,14 @@ import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analysis_server/src/protocol/protocol_internal.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 
 import 'integration_tests.dart';
 import 'protocol_matchers.dart';
-import 'package:analyzer_plugin/protocol/protocol_common.dart';
 
-/// Convenience methods for running integration tests.
-abstract class IntegrationTestMixin {
+/// Base implementation for running integration tests.
+abstract class IntegrationTest {
   Server get server;
 
   /// Return the version number of the analysis server.
@@ -39,10 +39,9 @@ abstract class IntegrationTestMixin {
   /// this request, but for which a response has not yet been sent, will not be
   /// responded to. No further responses or notifications will be sent after
   /// the response to this request has been sent.
-  Future sendServerShutdown() async {
+  Future<void> sendServerShutdown() async {
     var result = await server.send('server.shutdown', null);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Subscribe for services. All previous subscriptions are replaced by the
@@ -57,11 +56,11 @@ abstract class IntegrationTestMixin {
   /// subscriptions: List<ServerService>
   ///
   ///   A list of the services being subscribed to.
-  Future sendServerSetSubscriptions(List<ServerService> subscriptions) async {
+  Future<void> sendServerSetSubscriptions(
+      List<ServerService> subscriptions) async {
     var params = ServerSetSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('server.setSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Requests cancellation of a request sent by the client by id. This is
@@ -77,11 +76,10 @@ abstract class IntegrationTestMixin {
   /// id: String
   ///
   ///   The id of the request that should be cancelled.
-  Future sendServerCancelRequest(String id) async {
+  Future<void> sendServerCancelRequest(String id) async {
     var params = ServerCancelRequestParams(id).toJson();
     var result = await server.send('server.cancelRequest', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Reports that the server is running. This notification is issued once
@@ -99,10 +97,12 @@ abstract class IntegrationTestMixin {
   /// pid: int
   ///
   ///   The process id of the analysis server process.
-  late Stream<ServerConnectedParams> onServerConnected;
+  late final Stream<ServerConnectedParams> onServerConnected =
+      _onServerConnected.stream.asBroadcastStream();
 
   /// Stream controller for [onServerConnected].
-  late StreamController<ServerConnectedParams> _onServerConnected;
+  final _onServerConnected =
+      StreamController<ServerConnectedParams>(sync: true);
 
   /// Reports that an unexpected error has occurred while executing the server.
   /// This notification is not used for problems with specific requests (which
@@ -127,20 +127,22 @@ abstract class IntegrationTestMixin {
   ///
   ///   The stack trace associated with the generation of the error, used for
   ///   debugging the server.
-  late Stream<ServerErrorParams> onServerError;
+  late final Stream<ServerErrorParams> onServerError =
+      _onServerError.stream.asBroadcastStream();
 
   /// Stream controller for [onServerError].
-  late StreamController<ServerErrorParams> _onServerError;
+  final _onServerError = StreamController<ServerErrorParams>(sync: true);
 
   /// The stream of entries describing events happened in the server.
   ///
   /// Parameters
   ///
   /// entry: ServerLogEntry
-  late Stream<ServerLogParams> onServerLog;
+  late final Stream<ServerLogParams> onServerLog =
+      _onServerLog.stream.asBroadcastStream();
 
   /// Stream controller for [onServerLog].
-  late StreamController<ServerLogParams> _onServerLog;
+  final _onServerLog = StreamController<ServerLogParams>(sync: true);
 
   /// Reports the current status of the server. Parameters are omitted if there
   /// has been no change in the status represented by that parameter.
@@ -163,10 +165,11 @@ abstract class IntegrationTestMixin {
   ///
   ///   Note: this status type is deprecated, and is no longer sent by the
   ///   server.
-  late Stream<ServerStatusParams> onServerStatus;
+  late final Stream<ServerStatusParams> onServerStatus =
+      _onServerStatus.stream.asBroadcastStream();
 
   /// Stream controller for [onServerStatus].
-  late StreamController<ServerStatusParams> _onServerStatus;
+  final _onServerStatus = StreamController<ServerStatusParams>(sync: true);
 
   /// Return the errors associated with the given file. If the errors for the
   /// given file have not yet been computed, or the most recently computed
@@ -452,10 +455,9 @@ abstract class IntegrationTestMixin {
   /// Force re-reading of all potentially changed files, re-resolving of all
   /// referenced URIs, and corresponding re-analysis of everything affected in
   /// the current analysis roots.
-  Future sendAnalysisReanalyze() async {
+  Future<void> sendAnalysisReanalyze() async {
     var result = await server.send('analysis.reanalyze', null);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Sets the root paths used to determine which files to analyze. The set of
@@ -509,7 +511,7 @@ abstract class IntegrationTestMixin {
   ///   their package: URI's resolved using the normal pubspec.yaml mechanism.
   ///   If this field is absent, or the empty map is specified, that indicates
   ///   that the normal pubspec.yaml mechanism should always be used.
-  Future sendAnalysisSetAnalysisRoots(
+  Future<void> sendAnalysisSetAnalysisRoots(
       List<String> included, List<String> excluded,
       {Map<String, String>? packageRoots}) async {
     var params = AnalysisSetAnalysisRootsParams(included, excluded,
@@ -517,7 +519,6 @@ abstract class IntegrationTestMixin {
         .toJson();
     var result = await server.send('analysis.setAnalysisRoots', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Subscribe for general services (that is, services that are not specific
@@ -533,12 +534,11 @@ abstract class IntegrationTestMixin {
   /// subscriptions: List<GeneralAnalysisService>
   ///
   ///   A list of the services being subscribed to.
-  Future sendAnalysisSetGeneralSubscriptions(
+  Future<void> sendAnalysisSetGeneralSubscriptions(
       List<GeneralAnalysisService> subscriptions) async {
     var params = AnalysisSetGeneralSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('analysis.setGeneralSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Set the priority files to the files in the given list. A priority file is
@@ -564,11 +564,10 @@ abstract class IntegrationTestMixin {
   /// files: List<FilePath>
   ///
   ///   The files that are to be a priority for analysis.
-  Future sendAnalysisSetPriorityFiles(List<String> files) async {
+  Future<void> sendAnalysisSetPriorityFiles(List<String> files) async {
     var params = AnalysisSetPriorityFilesParams(files).toJson();
     var result = await server.send('analysis.setPriorityFiles', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Subscribe for services that are specific to individual files. All
@@ -601,12 +600,11 @@ abstract class IntegrationTestMixin {
   ///
   ///   A table mapping services to a list of the files being subscribed to the
   ///   service.
-  Future sendAnalysisSetSubscriptions(
+  Future<void> sendAnalysisSetSubscriptions(
       Map<AnalysisService, List<String>> subscriptions) async {
     var params = AnalysisSetSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('analysis.setSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Update the content of one or more files. Files that were previously
@@ -647,11 +645,10 @@ abstract class IntegrationTestMixin {
   ///
   ///   The options that are to be used to control analysis.
   @deprecated
-  Future sendAnalysisUpdateOptions(AnalysisOptions options) async {
+  Future<void> sendAnalysisUpdateOptions(AnalysisOptions options) async {
     var params = AnalysisUpdateOptionsParams(options).toJson();
     var result = await server.send('analysis.updateOptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Reports the paths of the files that are being analyzed.
@@ -665,10 +662,12 @@ abstract class IntegrationTestMixin {
   /// directories: List<FilePath>
   ///
   ///   A list of the paths of the files that are being analyzed.
-  late Stream<AnalysisAnalyzedFilesParams> onAnalysisAnalyzedFiles;
+  late final Stream<AnalysisAnalyzedFilesParams> onAnalysisAnalyzedFiles =
+      _onAnalysisAnalyzedFiles.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisAnalyzedFiles].
-  late StreamController<AnalysisAnalyzedFilesParams> _onAnalysisAnalyzedFiles;
+  final _onAnalysisAnalyzedFiles =
+      StreamController<AnalysisAnalyzedFilesParams>(sync: true);
 
   /// Reports closing labels relevant to a given file.
   ///
@@ -691,10 +690,12 @@ abstract class IntegrationTestMixin {
   ///   constructor/method calls and List arguments that span multiple lines.
   ///   Note that the ranges that are returned can overlap each other because
   ///   they may be associated with constructs that can be nested.
-  late Stream<AnalysisClosingLabelsParams> onAnalysisClosingLabels;
+  late final Stream<AnalysisClosingLabelsParams> onAnalysisClosingLabels =
+      _onAnalysisClosingLabels.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisClosingLabels].
-  late StreamController<AnalysisClosingLabelsParams> _onAnalysisClosingLabels;
+  final _onAnalysisClosingLabels =
+      StreamController<AnalysisClosingLabelsParams>(sync: true);
 
   /// Reports the errors associated with a given file. The set of errors
   /// included in the notification is always a complete list that supersedes
@@ -709,10 +710,11 @@ abstract class IntegrationTestMixin {
   /// errors: List<AnalysisError>
   ///
   ///   The errors contained in the file.
-  late Stream<AnalysisErrorsParams> onAnalysisErrors;
+  late final Stream<AnalysisErrorsParams> onAnalysisErrors =
+      _onAnalysisErrors.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisErrors].
-  late StreamController<AnalysisErrorsParams> _onAnalysisErrors;
+  final _onAnalysisErrors = StreamController<AnalysisErrorsParams>(sync: true);
 
   /// Reports that any analysis results that were previously associated with
   /// the given files should be considered to be invalid because those files
@@ -732,10 +734,12 @@ abstract class IntegrationTestMixin {
   /// files: List<FilePath>
   ///
   ///   The files that are no longer being analyzed.
-  late Stream<AnalysisFlushResultsParams> onAnalysisFlushResults;
+  late final Stream<AnalysisFlushResultsParams> onAnalysisFlushResults =
+      _onAnalysisFlushResults.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisFlushResults].
-  late StreamController<AnalysisFlushResultsParams> _onAnalysisFlushResults;
+  final _onAnalysisFlushResults =
+      StreamController<AnalysisFlushResultsParams>(sync: true);
 
   /// Reports the folding regions associated with a given file. Folding regions
   /// can be nested, but will not be overlapping. Nesting occurs when a
@@ -755,10 +759,12 @@ abstract class IntegrationTestMixin {
   /// regions: List<FoldingRegion>
   ///
   ///   The folding regions contained in the file.
-  late Stream<AnalysisFoldingParams> onAnalysisFolding;
+  late final Stream<AnalysisFoldingParams> onAnalysisFolding =
+      _onAnalysisFolding.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisFolding].
-  late StreamController<AnalysisFoldingParams> _onAnalysisFolding;
+  final _onAnalysisFolding =
+      StreamController<AnalysisFoldingParams>(sync: true);
 
   /// Reports the highlight regions associated with a given file.
   ///
@@ -779,10 +785,12 @@ abstract class IntegrationTestMixin {
   ///   some range. Note that the highlight regions that are returned can
   ///   overlap other highlight regions if there is more than one meaning
   ///   associated with a particular region.
-  late Stream<AnalysisHighlightsParams> onAnalysisHighlights;
+  late final Stream<AnalysisHighlightsParams> onAnalysisHighlights =
+      _onAnalysisHighlights.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisHighlights].
-  late StreamController<AnalysisHighlightsParams> _onAnalysisHighlights;
+  final _onAnalysisHighlights =
+      StreamController<AnalysisHighlightsParams>(sync: true);
 
   /// Reports the classes that are implemented or extended and class members
   /// that are implemented or overridden in a file.
@@ -804,10 +812,12 @@ abstract class IntegrationTestMixin {
   /// members: List<ImplementedMember>
   ///
   ///   The member defined in the file that are implemented or overridden.
-  late Stream<AnalysisImplementedParams> onAnalysisImplemented;
+  late final Stream<AnalysisImplementedParams> onAnalysisImplemented =
+      _onAnalysisImplemented.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisImplemented].
-  late StreamController<AnalysisImplementedParams> _onAnalysisImplemented;
+  final _onAnalysisImplemented =
+      StreamController<AnalysisImplementedParams>(sync: true);
 
   /// Reports that the navigation information associated with a region of a
   /// single file has become invalid and should be re-requested.
@@ -835,10 +845,12 @@ abstract class IntegrationTestMixin {
   ///   The delta to be applied to the offsets in information that follows the
   ///   invalidated region in order to update it so that it doesn't need to be
   ///   re-requested.
-  late Stream<AnalysisInvalidateParams> onAnalysisInvalidate;
+  late final Stream<AnalysisInvalidateParams> onAnalysisInvalidate =
+      _onAnalysisInvalidate.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisInvalidate].
-  late StreamController<AnalysisInvalidateParams> _onAnalysisInvalidate;
+  final _onAnalysisInvalidate =
+      StreamController<AnalysisInvalidateParams>(sync: true);
 
   /// Reports the navigation targets associated with a given file.
   ///
@@ -871,10 +883,12 @@ abstract class IntegrationTestMixin {
   ///
   ///   The files containing navigation targets referenced in the file. They
   ///   are referenced by NavigationTargets by their index in this array.
-  late Stream<AnalysisNavigationParams> onAnalysisNavigation;
+  late final Stream<AnalysisNavigationParams> onAnalysisNavigation =
+      _onAnalysisNavigation.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisNavigation].
-  late StreamController<AnalysisNavigationParams> _onAnalysisNavigation;
+  final _onAnalysisNavigation =
+      StreamController<AnalysisNavigationParams>(sync: true);
 
   /// Reports the occurrences of references to elements within a single file.
   ///
@@ -891,10 +905,12 @@ abstract class IntegrationTestMixin {
   /// occurrences: List<Occurrences>
   ///
   ///   The occurrences of references to elements within the file.
-  late Stream<AnalysisOccurrencesParams> onAnalysisOccurrences;
+  late final Stream<AnalysisOccurrencesParams> onAnalysisOccurrences =
+      _onAnalysisOccurrences.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisOccurrences].
-  late StreamController<AnalysisOccurrencesParams> _onAnalysisOccurrences;
+  final _onAnalysisOccurrences =
+      StreamController<AnalysisOccurrencesParams>(sync: true);
 
   /// Reports the outline associated with a single file.
   ///
@@ -923,10 +939,12 @@ abstract class IntegrationTestMixin {
   /// outline: Outline
   ///
   ///   The outline associated with the file.
-  late Stream<AnalysisOutlineParams> onAnalysisOutline;
+  late final Stream<AnalysisOutlineParams> onAnalysisOutline =
+      _onAnalysisOutline.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisOutline].
-  late StreamController<AnalysisOutlineParams> _onAnalysisOutline;
+  final _onAnalysisOutline =
+      StreamController<AnalysisOutlineParams>(sync: true);
 
   /// Reports the overriding members in a file.
   ///
@@ -943,10 +961,12 @@ abstract class IntegrationTestMixin {
   /// overrides: List<Override>
   ///
   ///   The overrides associated with the file.
-  late Stream<AnalysisOverridesParams> onAnalysisOverrides;
+  late final Stream<AnalysisOverridesParams> onAnalysisOverrides =
+      _onAnalysisOverrides.stream.asBroadcastStream();
 
   /// Stream controller for [onAnalysisOverrides].
-  late StreamController<AnalysisOverridesParams> _onAnalysisOverrides;
+  final _onAnalysisOverrides =
+      StreamController<AnalysisOverridesParams>(sync: true);
 
   /// Request that completion suggestions for the given offset in the given
   /// file be returned.
@@ -1062,12 +1082,11 @@ abstract class IntegrationTestMixin {
   /// subscriptions: List<CompletionService>
   ///
   ///   A list of the services being subscribed to.
-  Future sendCompletionSetSubscriptions(
+  Future<void> sendCompletionSetSubscriptions(
       List<CompletionService> subscriptions) async {
     var params = CompletionSetSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('completion.setSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// The client can make this request to express interest in certain libraries
@@ -1087,11 +1106,11 @@ abstract class IntegrationTestMixin {
   ///   suggestions. If one configured path is beneath another, the descendant
   ///   will override the ancestors' configured libraries of interest.
   @deprecated
-  Future sendCompletionRegisterLibraryPaths(List<LibraryPathSet> paths) async {
+  Future<void> sendCompletionRegisterLibraryPaths(
+      List<LibraryPathSet> paths) async {
     var params = CompletionRegisterLibraryPathsParams(paths).toJson();
     var result = await server.send('completion.registerLibraryPaths', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Clients must make this request when the user has selected a completion
@@ -1267,10 +1286,12 @@ abstract class IntegrationTestMixin {
   ///
   ///   If an AvailableSuggestion has relevance tags that match more than one
   ///   IncludedSuggestionRelevanceTag, the maximum relevance boost is used.
-  late Stream<CompletionResultsParams> onCompletionResults;
+  late final Stream<CompletionResultsParams> onCompletionResults =
+      _onCompletionResults.stream.asBroadcastStream();
 
   /// Stream controller for [onCompletionResults].
-  late StreamController<CompletionResultsParams> _onCompletionResults;
+  final _onCompletionResults =
+      StreamController<CompletionResultsParams>(sync: true);
 
   /// Reports the pre-computed, candidate completions from symbols defined in a
   /// corresponding library. This notification may be sent multiple times. When
@@ -1290,12 +1311,13 @@ abstract class IntegrationTestMixin {
   /// removedLibraries: List<int> (optional)
   ///
   ///   A list of library ids that no longer apply.
-  late Stream<CompletionAvailableSuggestionsParams>
-      onCompletionAvailableSuggestions;
+  late final Stream<CompletionAvailableSuggestionsParams>
+      onCompletionAvailableSuggestions =
+      _onCompletionAvailableSuggestions.stream.asBroadcastStream();
 
   /// Stream controller for [onCompletionAvailableSuggestions].
-  late StreamController<CompletionAvailableSuggestionsParams>
-      _onCompletionAvailableSuggestions;
+  final _onCompletionAvailableSuggestions =
+      StreamController<CompletionAvailableSuggestionsParams>(sync: true);
 
   /// Reports existing imports in a library. This notification may be sent
   /// multiple times for a library. When a notification is processed, clients
@@ -1310,11 +1332,13 @@ abstract class IntegrationTestMixin {
   /// imports: ExistingImports
   ///
   ///   The existing imports in the library.
-  late Stream<CompletionExistingImportsParams> onCompletionExistingImports;
+  late final Stream<CompletionExistingImportsParams>
+      onCompletionExistingImports =
+      _onCompletionExistingImports.stream.asBroadcastStream();
 
   /// Stream controller for [onCompletionExistingImports].
-  late StreamController<CompletionExistingImportsParams>
-      _onCompletionExistingImports;
+  final _onCompletionExistingImports =
+      StreamController<CompletionExistingImportsParams>(sync: true);
 
   /// Perform a search for references to the element defined or referenced at
   /// the given offset in the given file.
@@ -1548,10 +1572,11 @@ abstract class IntegrationTestMixin {
   ///
   ///   True if this is that last set of results that will be returned for the
   ///   indicated search.
-  late Stream<SearchResultsParams> onSearchResults;
+  late final Stream<SearchResultsParams> onSearchResults =
+      _onSearchResults.stream.asBroadcastStream();
 
   /// Stream controller for [onSearchResults].
-  late StreamController<SearchResultsParams> _onSearchResults;
+  final _onSearchResults = StreamController<SearchResultsParams>(sync: true);
 
   /// Format the contents of a single file. The currently selected region of
   /// text is passed in so that the selection can be preserved across the
@@ -2141,11 +2166,10 @@ abstract class IntegrationTestMixin {
   /// id: ExecutionContextId
   ///
   ///   The identifier of the execution context that is to be deleted.
-  Future sendExecutionDeleteContext(String id) async {
+  Future<void> sendExecutionDeleteContext(String id) async {
     var params = ExecutionDeleteContextParams(id).toJson();
     var result = await server.send('execution.deleteContext', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Request completion suggestions for the given runtime context.
@@ -2306,12 +2330,11 @@ abstract class IntegrationTestMixin {
   ///
   ///   A list of the services being subscribed to.
   @deprecated
-  Future sendExecutionSetSubscriptions(
+  Future<void> sendExecutionSetSubscriptions(
       List<ExecutionService> subscriptions) async {
     var params = ExecutionSetSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('execution.setSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Reports information needed to allow a single file to be launched.
@@ -2336,10 +2359,12 @@ abstract class IntegrationTestMixin {
   ///
   ///   A list of the Dart files that are referenced by the file. This field is
   ///   omitted if the file is not an HTML file.
-  late Stream<ExecutionLaunchDataParams> onExecutionLaunchData;
+  late final Stream<ExecutionLaunchDataParams> onExecutionLaunchData =
+      _onExecutionLaunchData.stream.asBroadcastStream();
 
   /// Stream controller for [onExecutionLaunchData].
-  late StreamController<ExecutionLaunchDataParams> _onExecutionLaunchData;
+  final _onExecutionLaunchData =
+      StreamController<ExecutionLaunchDataParams>(sync: true);
 
   /// Return server diagnostics.
   ///
@@ -2407,11 +2432,10 @@ abstract class IntegrationTestMixin {
   /// value: bool
   ///
   ///   Enable or disable analytics.
-  Future sendAnalyticsEnable(bool value) async {
+  Future<void> sendAnalyticsEnable(bool value) async {
     var params = AnalyticsEnableParams(value).toJson();
     var result = await server.send('analytics.enable', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Send information about client events.
@@ -2432,11 +2456,10 @@ abstract class IntegrationTestMixin {
   /// action: String
   ///
   ///   The value used to indicate which action was performed.
-  Future sendAnalyticsSendEvent(String action) async {
+  Future<void> sendAnalyticsSendEvent(String action) async {
     var params = AnalyticsSendEventParams(action).toJson();
     var result = await server.send('analytics.sendEvent', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Send timing information for client events (e.g. code completions).
@@ -2460,11 +2483,10 @@ abstract class IntegrationTestMixin {
   /// millis: int
   ///
   ///   The duration of the event in milliseconds.
-  Future sendAnalyticsSendTiming(String event, int millis) async {
+  Future<void> sendAnalyticsSendTiming(String event, int millis) async {
     var params = AnalyticsSendTimingParams(event, millis).toJson();
     var result = await server.send('analytics.sendTiming', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Return the description of the widget instance at the given location.
@@ -2578,12 +2600,11 @@ abstract class IntegrationTestMixin {
   ///
   ///   A table mapping services to a list of the files being subscribed to the
   ///   service.
-  Future sendFlutterSetSubscriptions(
+  Future<void> sendFlutterSetSubscriptions(
       Map<FlutterService, List<String>> subscriptions) async {
     var params = FlutterSetSubscriptionsParams(subscriptions).toJson();
     var result = await server.send('flutter.setSubscriptions', params);
     outOfTestExpect(result, isNull);
-    return null;
   }
 
   /// Reports the Flutter outline associated with a single file.
@@ -2601,76 +2622,11 @@ abstract class IntegrationTestMixin {
   /// outline: FlutterOutline
   ///
   ///   The outline associated with the file.
-  late Stream<FlutterOutlineParams> onFlutterOutline;
+  late final Stream<FlutterOutlineParams> onFlutterOutline =
+      _onFlutterOutline.stream.asBroadcastStream();
 
   /// Stream controller for [onFlutterOutline].
-  late StreamController<FlutterOutlineParams> _onFlutterOutline;
-
-  /// Initialize the fields in InttestMixin, and ensure that notifications will
-  /// be handled.
-  void initializeInttestMixin() {
-    _onServerConnected = StreamController<ServerConnectedParams>(sync: true);
-    onServerConnected = _onServerConnected.stream.asBroadcastStream();
-    _onServerError = StreamController<ServerErrorParams>(sync: true);
-    onServerError = _onServerError.stream.asBroadcastStream();
-    _onServerLog = StreamController<ServerLogParams>(sync: true);
-    onServerLog = _onServerLog.stream.asBroadcastStream();
-    _onServerStatus = StreamController<ServerStatusParams>(sync: true);
-    onServerStatus = _onServerStatus.stream.asBroadcastStream();
-    _onAnalysisAnalyzedFiles =
-        StreamController<AnalysisAnalyzedFilesParams>(sync: true);
-    onAnalysisAnalyzedFiles =
-        _onAnalysisAnalyzedFiles.stream.asBroadcastStream();
-    _onAnalysisClosingLabels =
-        StreamController<AnalysisClosingLabelsParams>(sync: true);
-    onAnalysisClosingLabels =
-        _onAnalysisClosingLabels.stream.asBroadcastStream();
-    _onAnalysisErrors = StreamController<AnalysisErrorsParams>(sync: true);
-    onAnalysisErrors = _onAnalysisErrors.stream.asBroadcastStream();
-    _onAnalysisFlushResults =
-        StreamController<AnalysisFlushResultsParams>(sync: true);
-    onAnalysisFlushResults = _onAnalysisFlushResults.stream.asBroadcastStream();
-    _onAnalysisFolding = StreamController<AnalysisFoldingParams>(sync: true);
-    onAnalysisFolding = _onAnalysisFolding.stream.asBroadcastStream();
-    _onAnalysisHighlights =
-        StreamController<AnalysisHighlightsParams>(sync: true);
-    onAnalysisHighlights = _onAnalysisHighlights.stream.asBroadcastStream();
-    _onAnalysisImplemented =
-        StreamController<AnalysisImplementedParams>(sync: true);
-    onAnalysisImplemented = _onAnalysisImplemented.stream.asBroadcastStream();
-    _onAnalysisInvalidate =
-        StreamController<AnalysisInvalidateParams>(sync: true);
-    onAnalysisInvalidate = _onAnalysisInvalidate.stream.asBroadcastStream();
-    _onAnalysisNavigation =
-        StreamController<AnalysisNavigationParams>(sync: true);
-    onAnalysisNavigation = _onAnalysisNavigation.stream.asBroadcastStream();
-    _onAnalysisOccurrences =
-        StreamController<AnalysisOccurrencesParams>(sync: true);
-    onAnalysisOccurrences = _onAnalysisOccurrences.stream.asBroadcastStream();
-    _onAnalysisOutline = StreamController<AnalysisOutlineParams>(sync: true);
-    onAnalysisOutline = _onAnalysisOutline.stream.asBroadcastStream();
-    _onAnalysisOverrides =
-        StreamController<AnalysisOverridesParams>(sync: true);
-    onAnalysisOverrides = _onAnalysisOverrides.stream.asBroadcastStream();
-    _onCompletionResults =
-        StreamController<CompletionResultsParams>(sync: true);
-    onCompletionResults = _onCompletionResults.stream.asBroadcastStream();
-    _onCompletionAvailableSuggestions =
-        StreamController<CompletionAvailableSuggestionsParams>(sync: true);
-    onCompletionAvailableSuggestions =
-        _onCompletionAvailableSuggestions.stream.asBroadcastStream();
-    _onCompletionExistingImports =
-        StreamController<CompletionExistingImportsParams>(sync: true);
-    onCompletionExistingImports =
-        _onCompletionExistingImports.stream.asBroadcastStream();
-    _onSearchResults = StreamController<SearchResultsParams>(sync: true);
-    onSearchResults = _onSearchResults.stream.asBroadcastStream();
-    _onExecutionLaunchData =
-        StreamController<ExecutionLaunchDataParams>(sync: true);
-    onExecutionLaunchData = _onExecutionLaunchData.stream.asBroadcastStream();
-    _onFlutterOutline = StreamController<FlutterOutlineParams>(sync: true);
-    onFlutterOutline = _onFlutterOutline.stream.asBroadcastStream();
-  }
+  final _onFlutterOutline = StreamController<FlutterOutlineParams>(sync: true);
 
   /// Dispatch the notification named [event], and containing parameters
   /// [params], to the appropriate stream.
diff --git a/pkg/analysis_server/test/integration/support/integration_tests.dart b/pkg/analysis_server/test/integration/support/integration_tests.dart
index 607aeb3b22f..f45b3e110bf 100644
--- a/pkg/analysis_server/test/integration/support/integration_tests.dart
+++ b/pkg/analysis_server/test/integration/support/integration_tests.dart
@@ -79,8 +79,7 @@ typedef MismatchDescriber = Description Function(
 typedef NotificationProcessor = void Function(String event, Map params);
 
 /// Base class for analysis server integration tests.
-abstract class AbstractAnalysisServerIntegrationTest
-    extends IntegrationTestMixin {
+abstract class AbstractAnalysisServerIntegrationTest extends IntegrationTest {
   /// Amount of time to give the server to respond to a shutdown request before
   /// forcibly terminating it.
   static const Duration SHUTDOWN_TIMEOUT = Duration(seconds: 60);
@@ -110,10 +109,6 @@ abstract class AbstractAnalysisServerIntegrationTest
 
   String dartSdkPath = path.dirname(path.dirname(Platform.resolvedExecutable));
 
-  AbstractAnalysisServerIntegrationTest() {
-    initializeInttestMixin();
-  }
-
   /// Return a future which will complete when a 'server.status' notification is
   /// received from the server with 'analyzing' set to false.
   ///
@@ -609,7 +604,7 @@ class Server {
   /// Start the server. If [profileServer] is `true`, the server will be started
   /// with "--observe" and "--pause-isolates-on-exit", allowing the observatory
   /// to be used.
-  Future start({
+  Future<void> start({
     required String dartSdkPath,
     int? diagnosticPort,
     String? instrumentationLogFile,
diff --git a/pkg/analysis_server/test/timing/timing_framework.dart b/pkg/analysis_server/test/timing/timing_framework.dart
index 07f7aded21c..7b8a548c49f 100644
--- a/pkg/analysis_server/test/timing/timing_framework.dart
+++ b/pkg/analysis_server/test/timing/timing_framework.dart
@@ -96,7 +96,7 @@ class TimingResult {
 
 /// The abstract class [TimingTest] defines the behavior of objects that measure
 /// the time required to perform some sequence of server operations.
-abstract class TimingTest extends IntegrationTestMixin {
+abstract class TimingTest extends IntegrationTest {
   /// The number of times the test will be performed in order to warm up the VM.
   static final int DEFAULT_WARMUP_COUNT = 10;
 
@@ -125,9 +125,6 @@ abstract class TimingTest extends IntegrationTestMixin {
   /// shutdown.
   bool skipShutdown = false;
 
-  /// Initialize a newly created test.
-  TimingTest();
-
   /// Return the number of iterations that should be performed in order to
   /// compute a time.
   int get timingCount => DEFAULT_TIMING_COUNT;
@@ -138,11 +135,10 @@ abstract class TimingTest extends IntegrationTestMixin {
 
   /// Perform any operations that need to be performed once before any
   /// iterations.
-  Future oneTimeSetUp() {
-    initializeInttestMixin();
+  Future<void> oneTimeSetUp() {
     server = Server();
     sourceDirectory = Directory.systemTemp.createTempSync('analysisServer');
-    var serverConnected = Completer();
+    var serverConnected = Completer<void>();
     onServerConnected.listen((_) {
       serverConnected.complete();
     });
@@ -159,7 +155,7 @@ abstract class TimingTest extends IntegrationTestMixin {
 
   /// Perform any operations that need to be performed once after all
   /// iterations.
-  Future oneTimeTearDown() {
+  Future<void> oneTimeTearDown() {
     return _shutdownIfNeeded().then((_) {
       sourceDirectory.deleteSync(recursive: true);
     });
@@ -213,7 +209,7 @@ abstract class TimingTest extends IntegrationTestMixin {
 
   /// Repeatedly execute this test [count] times, adding timing information to
   /// the given list of [times] if it is non-`null`.
-  Future _repeat(int count, List<int>? times) {
+  Future<void> _repeat(int count, List<int>? times) {
     var stopwatch = Stopwatch();
     return setUp().then((_) {
       stopwatch.start();
@@ -234,7 +230,7 @@ abstract class TimingTest extends IntegrationTestMixin {
   }
 
   /// Shut the server down unless [skipShutdown] is `true`.
-  Future _shutdownIfNeeded() {
+  Future<void> _shutdownIfNeeded() {
     if (skipShutdown) {
       return Future.value();
     }
diff --git a/pkg/analysis_server/tool/spec/codegen_inttest_methods.dart b/pkg/analysis_server/tool/spec/codegen_inttest_methods.dart
index 5864cb21be9..dfd35d995aa 100644
--- a/pkg/analysis_server/tool/spec/codegen_inttest_methods.dart
+++ b/pkg/analysis_server/tool/spec/codegen_inttest_methods.dart
@@ -90,32 +90,22 @@ class CodegenInttestMethodsVisitor extends DartCodegenVisitor
     writeln("import 'package:$packageName/protocol/protocol_generated.dart';");
     writeln(
         "import 'package:$packageName/src/protocol/protocol_internal.dart';");
-    writeln("import 'package:test/test.dart';");
-    writeln();
-    writeln("import 'integration_tests.dart';");
-    writeln("import 'protocol_matchers.dart';");
     for (var uri in api.types.importUris) {
       write("import '");
       write(uri);
       writeln("';");
     }
+    writeln("import 'package:test/test.dart';");
     writeln();
-    writeln('/// Convenience methods for running integration tests.');
-    writeln('abstract class IntegrationTestMixin {');
+    writeln("import 'integration_tests.dart';");
+    writeln("import 'protocol_matchers.dart';");
+    writeln();
+    writeln('/// Base implementation for running integration tests.');
+    writeln('abstract class IntegrationTest {');
     indent(() {
       writeln('Server get server;');
       super.visitApi();
       writeln();
-      docComment(toHtmlVisitor.collectHtml(() {
-        toHtmlVisitor.writeln('Initialize the fields in InttestMixin, and');
-        toHtmlVisitor.writeln('ensure that notifications will be handled.');
-      }));
-      writeln('void initializeInttestMixin() {');
-      indent(() {
-        write(fieldInitializationCode.join());
-      });
-      writeln('}');
-      writeln();
       docComment(toHtmlVisitor.collectHtml(() {
         toHtmlVisitor.writeln('Dispatch the notification named [event], and');
         toHtmlVisitor.writeln('containing parameters [params], to the');
@@ -151,16 +141,13 @@ class CodegenInttestMethodsVisitor extends DartCodegenVisitor
       toHtmlVisitor.translateHtml(notification.html);
       toHtmlVisitor.describePayload(notification.params, 'Parameters');
     }));
-    writeln('late Stream<$className> $streamName;');
+    writeln('late final Stream<$className> $streamName = '
+        '_$streamName.stream.asBroadcastStream();');
     writeln();
     docComment(toHtmlVisitor.collectHtml(() {
       toHtmlVisitor.write('Stream controller for [$streamName].');
     }));
-    writeln('late StreamController<$className> _$streamName;');
-    fieldInitializationCode.add(collectCode(() {
-      writeln('_$streamName = StreamController<$className>(sync: true);');
-      writeln('$streamName = _$streamName.stream.asBroadcastStream();');
-    }));
+    writeln('final _$streamName = StreamController<$className>(sync: true);');
     notificationSwitchContents.add(collectCode(() {
       writeln("case '${notification.longEvent}':");
       indent(() {
@@ -215,7 +202,7 @@ class CodegenInttestMethodsVisitor extends DartCodegenVisitor
           doCapitalize: true);
       futureClass = 'Future<$resultClass>';
     } else {
-      futureClass = 'Future';
+      futureClass = 'Future<void>';
     }
 
     writeln('$futureClass $methodName(${args.join(', ')}) async {');
@@ -249,7 +236,6 @@ class CodegenInttestMethodsVisitor extends DartCodegenVisitor
         writeln("return $resultClass.fromJson(decoder, 'result', result);");
       } else {
         writeln('outOfTestExpect(result, isNull);');
-        writeln('return null;');
       }
     });
     writeln('}');